The invention relates to an engine block of a diesel engine cast integrally with the cylinder head, with a number of cylinders in line, including an outer wall and a cylinder wall for each cylinder with a first cooling space for a liquid cooling medium between them and with a second cooling space on top of a cylinder ceiling with openings for gas exchange valves, the first cooling space enclosing all the cylinders entirely and extending upwards beyond the cylinder ceiling.
This design is also known as “Monoblock”. It avoids the drawbacks of the design with a separate cylinder head: The bolts joining the cylinder head to the engine block, and the gasket between them. It is therefore particularly suitable for Diesel engines of high performance. The high performance entails high pressures and needs intensive cooling by the liquid cooling medium, in particular around the cylinder ceilings. However, this design is demanding for the casting shop.
Such an engine is known from DE 19 38 134, for instance. Its cylinder walls are circumflown by a cooling liquid (usually water). In order to provide sufficient rigidity to the surrounding of the cylinder ceilings, these are incorporated in a through horizontal wall. But this divides the two cooling spaces, the cylinder walls are structurally vulnerable and not directly circumflown by the cooling liquid.
The German Utility Model 1 995 270 also discloses an engine in monoblock design, wherein the cylinder ceilings are united in a through plate. The cooling space enclosing the cylinder walls therefore does not reach beyond the cylinder ceilings all around. The sensible transition zone between cylinder walls and cylinder ceilings thus is not circumflown by the cooling water.
The Austrian Patent 382 429 discloses a further generic engine, including injection units in the cylinder head supplied with fuel by a common rail and with a first cooling space that rises beyond the cylinder ceilings, but without overlapping them. As can be seen, the cooling water passes from the first cooling space to the second cooling space (in the cylinder head) through a horizontal bore drilled from outside and blocked. This cannot provide a cooling water flow to the upper cooling space sufficient for a high performance engine.
The JP 07-071310 relates to a further engine in monoblock design. According to FIG. 3, the first cooling space overlaps the cylinder ceiling in the region of the valves, but only slightly. In order to achieve the desired improvement of structural strength and of cooling, overlap must coincide with the width of the gaps between adjacent cylinders around the cylinder walls which increases from top to bottom.
DE 100 33 271 B4 relates to the casting core for the cooling jacket of an engine of conventional design, not monoblock. In this design the problem of the transition between cylinder wall and cylinder ceiling does not arise. The described casting process uses inserts, but inserted into the core. This is time consuming, limiting the design and the insert must be destroyed when unmolding the cast part.
When preparing the casting mould for such an engine block, the core parts corresponding to the cooling space around the cylinder wall must be made with a draft angle of some degrees of angle. This is necessary in order to enable the core parts to be extracted from the core mould (also called core box) without being damaged. This draft angle is always featured, even if not visible in conventional drawings because it is only of some degrees of angle. It is of particular importance with very thin core parts corresponding to the regions of the water space between adjacent cylinders. Thin core parts are very fragile.
The draft angle of the core part for this region entails that it is wider near the cylinder ceiling than at its lower end. This has the consequence that the wall thickness of the cylinder wall is smaller on top, in the particularly vulnerable transitional region between cylinder wall and cylinder ceiling. This vulnerable region limits the specific performance of an engine.